I said 'no', but then I backed down. change your original position
I turned down his offer. refuse an offer (say 'no thank you')
 
The vet put down my dog. kill an animal which is suffering
 
My car broke down on the motorway. stop working (machine)
 
The noise died down. become quieter
 
He really let me down. disappoint sb
 
I'll settle down when I'm 30. start living a sensible, adult life
 
He should slow down. do sth more slowly
 
The prime minister had to stand down after the scandal. resign from a position of power
 
Please calm down.

become less excited/angry